feat: Add ability to inspect build information and features at runtime

Also re-adds ability to inspect used features

src/build_metadata/Cargo.toml

@@ -2,6 +2,7 @@
 name = "conduwuit_build_metadata"
 description.workspace = true
 edition.workspace = true
+homepage.workspace = true
 license.workspace = true
 readme.workspace = true
 repository.workspace = true
@@ -27,6 +28,6 @@ crate-type = [
 
 [build-dependencies]
 built = { version = "0.8", features = [] }
-
+cargo_metadata = { version = "0.23.1" }
 [lints]
 workspace = true

src/build_metadata/build.rs

@@ -1,5 +1,9 @@
-use std::process::Command;
+use std::{
+	collections::BTreeMap, env, fmt::Write as FmtWrite, fs, io::Write, path::Path,
+	process::Command,
+};
 
+use cargo_metadata::MetadataCommand;
 fn run_git_command(args: &[&str]) -> Option<String> {
 	Command::new("git")
 		.args(args)
@@ -11,12 +15,60 @@ fn run_git_command(args: &[&str]) -> Option<String> {
 		.filter(|s| !s.is_empty())
 }
 fn get_env(env_var: &str) -> Option<String> {
-	match std::env::var(env_var) {
+	match env::var(env_var) {
 		| Ok(val) if !val.is_empty() => Some(val),
 		| _ => None,
 	}
 }
 fn main() {
+	println!("cargo:rerun-if-changed=Cargo.toml");
+
+	let manifest_dir = env::var("CARGO_MANIFEST_DIR").unwrap(); // Cargo.toml path
+	let manifest_path = Path::new(&manifest_dir).join("Cargo.toml");
+
+	let metadata = MetadataCommand::new()
+		.manifest_path(&manifest_path)
+		.no_deps()
+		.exec()
+		.expect("failed to parse `cargo metadata`");
+
+	let workspace_packages = metadata
+		.workspace_members
+		.iter()
+		.map(|package| {
+			let package = metadata.packages.iter().find(|p| p.id == *package).unwrap();
+			println!("cargo:rerun-if-changed={}", package.manifest_path.as_str());
+			package
+		})
+		.collect::<Vec<_>>();
+
+	// Extract available features from workspace packages
+	let mut available_features: BTreeMap<String, Vec<String>> = BTreeMap::new();
+	for package in &workspace_packages {
+		let crate_name = package
+			.name
+			.trim_start_matches("conduwuit-")
+			.replace('-', "_");
+		let features: Vec<String> = package.features.keys().cloned().collect();
+		if !features.is_empty() {
+			available_features.insert(crate_name, features);
+		}
+	}
+
+	// Generate Rust code for available features
+	let features_code = generate_features_code(&available_features);
+	let features_dst =
+		Path::new(&env::var("OUT_DIR").expect("OUT_DIR not set")).join("available_features.rs");
+	let mut features_file = fs::File::create(features_dst).unwrap();
+	features_file.write_all(features_code.as_bytes()).unwrap();
+
+	let dst = Path::new(&env::var("OUT_DIR").expect("OUT_DIR not set")).join("pkg.json");
+
+	let mut out_file = fs::File::create(dst).unwrap();
+	out_file
+		.write_all(format!("{workspace_packages:?}").as_bytes())
+		.unwrap();
+
 	// built gets the default crate from the workspace. Not sure if this is intended
 	// behavior, but it's what we want.
 	built::write_built_file().expect("Failed to acquire build-time information");
@@ -91,3 +143,30 @@ fn main() {
 	println!("cargo:rerun-if-env-changed=GIT_REMOTE_URL");
 	println!("cargo:rerun-if-env-changed=GIT_REMOTE_COMMIT_URL");
 }
+
+fn generate_features_code(features: &BTreeMap<String, Vec<String>>) -> String {
+	let mut code = String::from(
+		r#"
+/// All available features for workspace crates
+pub const WORKSPACE_FEATURES: &[(&str, &[&str])] = &[
+"#,
+	);
+
+	for (crate_name, feature_list) in features {
+		write!(code, "    (\"{crate_name}\", &[").unwrap();
+		for (i, feature) in feature_list.iter().enumerate() {
+			if i > 0 {
+				code.push_str(", ");
+			}
+			write!(code, "\"{feature}\"").unwrap();
+		}
+		code.push_str("]),\n");
+	}
+
+	code.push_str(
+		r#"];
+"#,
+	);
+
+	code
+}

src/build_metadata/mod.rs

@@ -2,6 +2,10 @@ pub mod built {
 	include!(concat!(env!("OUT_DIR"), "/built.rs"));
 }
 
+// Include generated available features
+// This provides: pub const WORKSPACE_FEATURES: &[(&str, &[&str])]
+include!(concat!(env!("OUT_DIR"), "/available_features.rs"));
+
 pub static GIT_COMMIT_HASH: Option<&str> = option_env!("GIT_COMMIT_HASH");
 
 pub static GIT_COMMIT_HASH_SHORT: Option<&str> = option_env!("GIT_COMMIT_HASH_SHORT");